//===- llvm/Support/type_traits.h - Simplfied type traits -------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file provides useful additions to the standard type_traits library.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_SUPPORT_TYPE_TRAITS_H
#define LLVM_SUPPORT_TYPE_TRAITS_H

#include <type_traits>
#include <utility>

#ifndef __has_feature
#define LLVM_DEFINED_HAS_FEATURE
#define __has_feature(x) 0
#endif

namespace llvm {

/// isPodLike - This is a type trait that is used to determine whether a given
/// type can be copied around with memcpy instead of running ctors etc.
template<typename T> struct isPodLike {
    // std::is_trivially_copyable is available in libc++ with clang, libstdc++
    // that comes with GCC 5.
#if (__has_feature(is_trivially_copyable) && defined(_LIBCPP_VERSION)) || (defined(__GNUC__) && __GNUC__ >= 5)
    // If the compiler supports the is_trivially_copyable trait use it, as it
    // matches the definition of isPodLike closely.
    static const bool value = std::is_trivially_copyable<T>::value;
#elif __has_feature(is_trivially_copyable)
    // Use the internal name if the compiler supports is_trivially_copyable but we
    // don't know if the standard library does. This is the case for clang in
    // conjunction with libstdc++ from GCC 4.x.
    static const bool value = __is_trivially_copyable(T);
#else
    // If we don't know anything else, we can (at least) assume that all non-class
    // types are PODs.
    static const bool value = !std::is_class<T>::value;
#endif
};

// std::pair's are pod-like if their elements are.
template<typename T, typename U> struct isPodLike<std::pair<T, U>> { static const bool value = isPodLike<T>::value && isPodLike<U>::value; };

/// \brief Metafunction that determines whether the given type is either an
/// integral type or an enumeration type.
///
/// Note that this accepts potentially more integral types than is_integral
/// because it is based on merely being convertible implicitly to an integral
/// type.
template<typename T> class is_integral_or_enum {
    typedef typename std::remove_reference<T>::type UnderlyingT;

public:
    static const bool value = !std::is_class<UnderlyingT>::value && // Filter conversion operators.
                              !std::is_pointer<UnderlyingT>::value && !std::is_floating_point<UnderlyingT>::value
                              && std::is_convertible<UnderlyingT, unsigned long long>::value;
};

/// \brief If T is a pointer, just return it. If it is not, return T&.
template<typename T, typename Enable = void> struct add_lvalue_reference_if_not_pointer { typedef T &type; };

template<typename T> struct add_lvalue_reference_if_not_pointer<T, typename std::enable_if<std::is_pointer<T>::value>::type> { typedef T type; };

/// \brief If T is a pointer to X, return a pointer to const X. If it is not,
/// return const T.
template<typename T, typename Enable = void> struct add_const_past_pointer { typedef const T type; };

template<typename T> struct add_const_past_pointer<T, typename std::enable_if<std::is_pointer<T>::value>::type> {
    typedef const typename std::remove_pointer<T>::type *type;
};

} // namespace llvm

// If the compiler supports detecting whether a class is final, define
// an LLVM_IS_FINAL macro. If it cannot be defined properly, this
// macro will be left undefined.
#if __cplusplus >= 201402L
#define LLVM_IS_FINAL(Ty) std::is_final<Ty>()
#elif __has_feature(is_final) || LLVM_GNUC_PREREQ(4, 7, 0)
#define LLVM_IS_FINAL(Ty) __is_final(Ty)
#endif

#ifdef LLVM_DEFINED_HAS_FEATURE
#undef __has_feature
#endif

#endif
